A typical power steering system in an automotive vehicle comprises a pump that supplies pressurized hydraulic fluid to a steering gear assembly. Fluid is supplied to the pump by a reservoir and is returned to the reservoir from the steering gear assembly. The reservoir commonly includes a filter to remove particulate debris that might otherwise damage the pump or gear assembly.
A problem occurs when air becomes trapped in the hydraulic fluid. Entrained air may cause cavitation in the pump that results in noisy operation. Also, entrained air may interfere with optimum operation of the pump and gear and may even cause damage thereto. One concern involves displacement of the fluid during sharp turns of the vehicle, commonly referred to as sloshing. To provide uninterrupted fluid flow, it is common practice to provide a large and deep volume of fluid within the reservoir and to strategically locate the outlet to assure a continuous supply of fluid despite variations in the liquid level. Another source of entrained air is a attributed to air leakage through seals in the pump and gear assembly. Again, a large and deep volume of fluid allows entrained air to diffuse out before being recirculated. However, the dimensions of the reservoir are dictated by spacial constraints within the engine compartment of the vehicle. Under certain situations, the available space permits only a relatively shallow volume that is not suited for reservoirs of conventional design.
Therefore, a need exists for a hydraulic fluid reservoir that assures a continuous flow of fluid from the reservoir, while removing particulate debris and entrained air from the fluid, without necessitating a large and deep volume of fluid, thereby allowing the size, and particularly the height, of the reservoir to be reduced. In an automotive power steering system, the reservoir needs to remove entrained air and provide an air-free fluid flow despite sloshing that occurs during turns, so as to prevent cavitation or diminished performance in the pump or steering gear assembly